This invention relates to circuitry for converting a DC voltage of one magnitude to a DC voltage of another magnitude and more particularly to a transformer coupled double-ended, push-pull inverter.
Transformer coupled double-ended converter/inverter circuits are well known and in their simplest form comprise two switching devices which are alternately turned on and off periodically. These switching devices comprised of, for example, switching transistors are coupled to opposite ends of the primary winding of a power transformer whose center tap is connected to a source of DC supply potential. An oscillator circuit is utilized to drive the switching transistors at a predetermined operating frequency whereupon an AC signal is developed in the secondary winding of the transformer at twice the oscillator frequency which upon being rectified and filtered, provides a DC voltage of a desired magnitude.
One of the major problems involved in such circuitry, however, is the reduction of any unbalance in the currents flowing alternately in two halves of push-pull circuit configuration. One known means comprises matching the transistor characteristics of the alternately switched transistors or by using transistors having a sufficient signal capacity to tolerate the high currents generated by saturation of the transformer core. Other techniques have included inserting an inductor into the main current path of the switching transistors to inhibit rapid current rises due to saturation of the transformer.
It is an object of the present invention, therefore, to provide a relatively simple and inexpensive means for balancing the currents flowing through alternately conducting switching devices of a push-pull DC to DC inverter.
It is a further object of the present invention to provide a means of balancing current flow in the switching devices of a pulse width modulated double-ended DC to DC converter/inverter.